1. Field of the Invention
The present invention relates to an image forming apparatus such as electrophotographic printers, and more particularly to an image forming apparatus having a function of displaying consumable usage.
2. Description of the Related Art
Usage of consumables in an image forming apparatus may be determined in a variety of ways and displayed on a display of the apparatus. For example, a remaining amount of toner in a toner cartridge can be estimated based on an accumulated number of dots that have been printed, an amount of toner consumed for printing each dot, and an initial amount of toner held in the toner cartridge. Some conventional apparatuses are capable of detecting when an amount of remaining toner decreases below a predetermined level.
The amount of toner consumed in printing varies depending on the printing duty and types of images. This implies that the amount of toner consumed varies from dot to dot, and therefore the estimated remaining amount of toner may differ from an actual remaining amount of toner. For example, when a considerable amount of toner remains in the toner cartridge, a message “toner is empty” may be displayed, or when the toner cartridge is empty of toner, a message “considerable amount of toner exists” may be displayed. Moreover, for color printers, the toner usage is different depending on the color.